A number of prior art devices have been disclosed in the prior art for applying a herbicide to weeds in a field which have grown taller than the crop. One applicator which has been introduced recently and has become very popular is a "rope wick" applicator. A rope-wick applicator is disclosed in U.S. Pat. No. 4,187,638 to Hardy et al. This type of applicator uses an elongate hollow body through which portions of nylon rope extend and act as wicks. While the rope wick applicator has been used successfully, there are a number of problems associated with its use. As disclosed in an article entitled "Make No Mistake: Rope-Wick Applicators Take Management" appearing in the May, 1980 issue of Progressive Farmer at page 34, there are a number of problems which occur with this type of applicator. Chief among these problems is the dripping from the rope or the failure of the herbicide to wick in the ropes. In addition, the ropes have been pulled loose during use and there is only a limited wiping surface. Another applicator which uses ropes is manufactured by BoBar Company located at 101 South Main, Hale Center, Tex. This applicator consists of a number of ropes which are hung parallel to the direction of travel between two manifolds. An additional disadvantage of this device is that the manifolds bend the tall weeds away from the ropes so that the ropes may not contact these weeds.
Another type of commercial device disclosed in the prior art is a roller applicator. One such device is manufactured by Irrigation Specialties, Inc., Scottsbluff, Nebr. 69361. This device has an elongate body around which a carpet is rolled. As the device is transported through the field, the carpet roll is rotated and the chemical is first sprayed onto the outside of the roll from where the chemical is then wiped onto the tall weeds. Another commercial device is a recirculating sprayer such as manufactured by Sprayrite Manufacturing Company of West Helena, Arkansas. With this device, a plurality of spray heads direct the herbicide onto the plants. The spray which does not contact the plants is collected on a collection board and pumped back to the sprayer nozzles. This relatively expensive device suffered from a number of problems due to its complexity. Another type of recirculating sprayer was once manufactured by the Kuker Company of Omaha, Nebraska. This device included spray nozzles which saturated a canvas exterior of the boom which contacted the weeds. Herbicide which was not wiped from the canvas was recirculated to the spray nozzles.
There have also been disclosed in the prior art devices which have a perforated pipe covered with cloth which wipe across the weeds. Such devices are disclosed in U.S. Pat. Nos. 3,320,694 to Biron and 4,019,278 to McKirdy.
Besides use in a field, weed killing liquid applicators have also been disclosed for lawn use. For example, in U.S. Pat. No. 3,198,396 to Bailey, a trough mounted for movement over the grass includes a cloth portion which contacts the weeds. Similar to the device disclosed in Bailey and the roller applications disclosed above, is a device disclosed in U.S. Pat. No. 3,651,600 to Ewing. The device disclosed in this patent includes a tube mounted for rotation about the grass having a carpet cover. As the tube and carpet rotate, herbicide is absorbed by the cover through holes in the tube. An applicator which contacts the ground and has baffles to prevent the liquid from flowing to one side is disclosed in U.S. Pat. No. 2,551,096 to Chittick. The use of an air valve to control the flow rate of liquid through a porous weed applicator member has also been disclosed in U.S. Pat. No. 3,184,888 to Fruth et al.
While the prior art does contain a number of weed applicators, including applicators which have been commercially successful, a number of disadvantages are associated with these devices. For example, applicators which have been disclosed for use in a field are unduly complicated and expensive. In addition, the disclosed applicators may drip herbicide onto crops inadvertently. Another problem with prior art applicators is that often difficult maintenance is required. With regard to the applicators using spray nozzles, the use of these applicators during windy conditions is prohibited.